The present invention relates to an engine oil degradation judging method and apparatus for a diesel engine.
When a diesel engine is used, foreign substances are mixed with an engine oil with the passage of time. The foreign substances mainly include soot generated by the combustion of a fuel in the engine. When the amount of the soot contained in the engine oil is increased, lubricating properties are deteriorated and the internal wall of the engine or the like is damaged. More specifically, the performance of the engine oil is deteriorated by the mixture of the soot. Therefore, it is necessary to exchange the engine oil at a proper time.
In most cases, conventionally, the exchange of the engine oil is determined to be carried out when a running distance reaches a predetermined value (for example, 5000 Km). In a conventional diesel engine which does not have an electronic control type, there has been known a correlation between each of an engine speed, an injection pressure, a load (a fuel injection amount), an engine oil temperature and the like, and the amount of generated soot.
Accordingly, it is possible to estimate the amount of the soot contained in the engine oil depending on factors based on the correlation. The running distance at which the engine oil is to be exchanged is determined based on such an estimation.
For other techniques for giving a notice of the time that the engine oil is to be exchanged, a running distance and a load are monitored to give a notice, a degradation weighting factor is determined depending on an engine oil temperature and an engine speed and a running distance is corrected based on the factor to give a notice (Japanese Patent Application Laid-Open No. Sho 59-43299), a notice is given in consideration of the content of soot, the degree of an increase in a viscosity, a decrease in a total base number and the like (Japanese Patent Application Laid-Open No. 2000-227018).
However, the conventional art has the following problems.
For a first problem, the amount of the generated soot is calculated based on the correlation with the engine speed or the like and the calculation is not very accurate. In consideration of safety, therefore, a shorter distance than a running distance corresponding to the amount of generation thus calculated is determined as a running distance at which an oil is to be exchanged.
More specifically, the oil exchange is to be carried out earlier. Therefore, the engine oil is discarded irrespective of the residual lifetime of the engine oil which can be still used. Consequently, the resources are consumed wastefully and a cost is increased.
For a second problem, a diesel engine which is electronically controlled by a computer has a small correlation between an engine speed, an injection pressure or the like and the amount of the generated soot.
The calculation of the amount of the generated soot with the use of the conventional correlation does not correspond to actual conditions.
In a conventional diesel engine which is not controlled electronically, an injection pressure, an injection timing and the like are spontaneously determined corresponding to the mechanical operating situations of the engine (for example, whether the engine speed is high or low, and the like). Therefore, there is a correlation with the amount of the generated soot. In the electronic control, however, the injection pressure or the like is not always restrained by the mechanical operating situations of the engine but is optionally controlled depending on operating conditions. Therefore, the conventional correlation is not recognized.
The present invention has an object to solve the problems described above.
The first object of the invention is to be able to judge degradation in an engine oil more accurately than that in the conventional art. The present invention is based on the newly found phenomenon (correlation) in which the amount of soot generation in the diesel engine can be obtained more precisely than that in the conventional art.
The second object of the invention is to judge the oil degradation based on the amount of soot accumulated in the engine oil and to be able to use the engine oil until the lifetime of the oil is almost completed (the resources can be utilized effectively). Conventionally, the oil exchange has been carried out earlier based on a running distance. In many cases, therefore, the oil which can be still used is discarded.
The third object of the invention is to decrease the number of times of the oil exchange and to enhance maintenance properties with a reduction in a cost.
The fourth object of the invention is to inform a driver of a time that the oil exchange is to be carried out, displaying an oil exchange alarm on the display device of judgement result in response to an oil degradation decision output.
In order to solve the aforesaid subjects, the present invention provides a judging method of engine oil degradation to be carried out by obtaining an amount of soot generation in a diesel engine, comprising the steps of, calculating oil degradation value in the current injection by the injection end point in the case of the injection end point is set before the predetermined oil degradation degree dispersion point, calculating oil degradation value in the current injection by the injection end point as well as an injection amount after an oil degradation degree dispersion point in the case of the injection end point is set after the predetermined oil degradation degree dispersion point and accumulating oil degradation value in the current injection, thereby oil degradation is judged.
Moreover, the present invention provides an engine oil degradation judging apparatus in which a signal from a sensor for detecting a signal required for obtaining an injection end point is inputted, comprising a map storage portion for storing at least a first map for obtaining oil degradation value in the current injection by the injection end point in the case of the injection end point is set before a predetermined oil degradation degree dispersion point and a second map for obtaining oil degradation value in the current injection by the injection end point as well as an injection amount after an oil degradation degree dispersion point in the case of the injection end point is set after the predetermined oil degradation degree dispersion point, a current injection degradation value portion for obtaining an oil degradation value in the injection from the first or second map in every fuel injection and for storing the same value. a cumulative degradation value portion for cumulatively adding the value of the current injection degradation value portion to obtain a cumulative degradation value every time the injection is ended and for storing the same value, and an oil degradation judging portion for judging oil degradation based on the cumulative degradation value, thereby a judgement signal is output.
The oil degradation judging portion of the engine oil degradation judging apparatus includes a residual lifetime ratio portion for calculating a residual lifetime ratio representing a rate of a difference between a maximum allowable degradation value and a cumulative degradation value to a maximum allowable degradation value and for storing the residual lifetime ratio, and an oil exchange alarm generation value portion for storing a predetermined oil exchange alarm generation value for deciding whether or not an oil exchange alarm is given as compared with the residual lifetime ratio.
For an apparatus to be operated in response to the decision output of the engine oil degradation judging apparatus, furthermore, it is also possible to comprise a display device of judgement result to display judgement result including an oil exchange alarm in response to a judgement output.